Before I got home broadband (prolly about 6 months ago) my mobile broadband wad doing just that with vodafone packs you get off ebay. I had a look and the prices on ebay are good again, vodafone have new datapacks and one of them has a double data bonus for the weekends, sweet.
Buy packs off ebay…https://www.ebay.com.au/itm/Vodafone-40-Prepaid-Starter-Pack...
…notice the type of pack, it doesnt determine a plan type, you get to pick. You pick the 365 days or whatever it is and then use all the credit to buy data packs….https://www.vodafone.com.au/prepaid/add-ons
…notice the $5 for 4gig gets a bonus 4gig on the weekends, nice. Keep in mind I havent done this in months, but….back then 1 day was actually 2 days, it would cut off at the next midnight. So if you charged on friday arvo it would run out at midnight saturday. Another thing was I found out by accident that if you charged at just past midnight you got a new charge that kept the remaining data and lasted another 2 days.
And yes, I used a mobile broadband usb thingie.
Mixing the above with deals like this was the go, hope that helps.

Call Aldi and have them do it, if you call Vodafone, there is chance they just disconnect you and your phone number goes out into the ether, never to be called again. Or for X many years when it goes back into rotation.

I'm guessing the $50 Starter Kit can be activated on many different plans like the Coles one several weeks ago. And if activated on Prepaid Mobile Broadband option its possible to get 35GB (180 days expiry). In this case its $25 but comes with $20 Netflix Gift Card